Linear drive apparatus

ABSTRACT

The conventional linear drive apparatus has the problem that in constructing a linear motor of a multiphase structure by connecting a plurality of armature units, the length of the armature becomes longer in proportion to the number of the phases, thus limiting the locations where the apparatus can be installed. The problem is solved by a linear drive apparatus comprising a plurality of armature units  3  formed by a magnetic material on which a conductor coil  4  is disposed, and an armature comprising an arrangement of the armature units  3 . The armature units  3  comprise a plurality of opposing portions having opposing magnetic pole teeth. The magnetic pole teeth of adjacent opposing portions are arranged in an interdigitated manner. A secondary member  6  is disposed between magnetic pole teeth of the opposing portions. The armature units  3  comprise the coil  4  arranged on opposite sides thereof in an alternating manner.

The present application is a continuation of application Ser. No.10/639,484, filed Aug. 13, 2003, the contents of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a drive apparatus driven byelectromagnetic force.

In recent years, linear drive apparatus (linear motors) are increasinglyemployed as the drive source in semiconductor manufacturing equipment. Avariety of structures have been proposed for such linear motors. Forexample, JP Patent Publication (Unexamined Application) No. 2001-28875(to be hereafter referred to as Prior Art 1) discloses a linear motorthat is of a multiphase structure using a single coil in order tofacilitate production, attain reduction in size, and improve powerefficiency. In this linear motor, the armature comprises cores of twokinds of shapes that are arranged in a manner such that the two shapesalternate.

(Patent Literature 1)

JP Patent Publication (Unexamined Application) No. 2001-28875 (FIG. 4).

In this example, where a plurality of armature units are connected toform a multiphase linear motor, the length of the coil becomes longer inproportion to the number of phases, thus limiting the locations wherethe motor can be installed.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a linear motor of amultiphase structure whose length is reduced by decreasing the distancebetween armatures.

In one aspect, the invention provides a linear drive apparatuscomprising:

a plurality of armature units each comprising a magnetic material onwhich a coil made of a conductor is disposed; and

an armature comprising the multiple armature units arranged in a row,wherein

each armature unit comprises a plurality of opposing portions comprisingopposing magnetic pole teeth, the magnetic pole teeth being arranged inan interdigitated manner between adjacent opposing portions, wherein asecondary member is disposed between the magnetic pole teethconstituting the opposing portions, and wherein the armature unitscomprise coils disposed at at least two locations thereof.

In another aspect, the invention provides a linear drive apparatuscomprising:

a plurality of armature units each comprising a magnetic material onwhich a coil made of a conductor is disposed; and

an armature comprising the multiple armature units arranged in a row,wherein

each armature unit comprises a plurality of opposing portions eachcomprising opposing magnetic pole teeth, the magnetic pole teeth beingarranged in an interdigitated manner between adjacent opposing portions,wherein a secondary member is disposed between the magnetic pole teethconstituting the opposing portions, and wherein the armature unitscomprise coils each disposed at one side alternately.

In another aspect, the invention provides a linear drive apparatuscomprising:

a plurality of armature units each comprising a magnetic material onwhich a coil made of a conductor is disposed;

an armature comprising the multiple armature units; and

a secondary member comprising a flat board having a plurality of magnetsor a flat board made of a magnetic material and having an irregularsurface, wherein

the armature units comprise first and second magnetic poles, the firstmagnetic poles having a magnetic pole tooth disposed in one directionand a magnetic pole tooth disposed in another direction from theviewpoint of the secondary member, the magnetic pole teeth beingarranged alternately, the second magnetic poles having a magnetic poletooth disposed in one direction and a magnetic pole tooth disposed inanother direction from the viewpoint of the secondary member, themagnetic pole teeth being arranged alternately, wherein the armatureunits comprise coils each disposed at one side alternately.

Other features of the invention are described in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall view of a second embodiment of the invention.

FIG. 2 shows the structure of a linear motor used in a comparativeexample.

FIG. 3 is an overall view of the linear motor used in the comparativeexample.

FIG. 4 is an overall view of a first embodiment of the invention.

DESCRIPTION OF THE INVENTION

FIGS. 2 and 3 schematically show the structure of a linear motor in acomparative example to illustrate the operation and effects of theinvention. FIG. 2(a) illustrates the flow of the magnetic flux in thelinear motor. FIG. 2(b) is an overall view of the linear motor. Asecondary member of the linear motor is formed substantially in theshape of a flat plate, in which a plurality of permanent magnets 34 arearranged such that their N and S poles alternate. An armature unit 3constitutes a primary side (comprised of a magnetic material on which acoil is wound) of the linear motor, and it comprises cores 51 and 52,and an armature coil 4 made of a conductor. The coil 4 is disposed atthe bottom side of the cores 51 and 52. The cores 51 and 52 are made ofa magnetic material. In the armature unit 3, upper and lower magneticpole teeth are arranged in an interdigitated manner. An upper magneticpole tooth 11 a and a lower magnetic pole tooth 21 b of the core 51 aredefined as a first opposing portion. A lower magnetic pole tooth 12 band an upper magnetic pole tooth 22 a of the core 52 are defined as asecond opposing portion. Thus, in the armature 3, a (2n−1)th core formsthe first opposing portion and a (2n)th core forms the second opposingportion (where n=1, 2, 3, . . . ). In each opposing portion of the cores51 and 52, a predetermined gap is provided between the upper pole toothand the lower pole tooth. As the secondary member 6 is passed throughthe gap, the secondary member 6 is arranged between the pole teeth 11 aand 21 b of the first opposing portion and between the pole teeth 12 band 22 a of the second opposing portion. As a single-phase AC current iscaused to flow in the coil 4 in accordance with the relative position ofthe secondary member 6 and the armature 3, a magnetic flux flows in thegap between the upper pole tooth and the lower pole tooth of eachopposing portion of the linear motor upwards and downwards alternately.The directions of the magnetic flux flowing in the first and secondopposing portions are reversed alternately. The magnetic flux flowing inthe first and second opposing portions and the magnetic flux created bythe permanent magnet 34 act upon one another. This interaction createsan electromagnetic drive force in the secondary member 6 in thedirection of x, so that the secondary member 6 executes a reciprocatingmotion. Magnetic poles 1 on one side of the armature unit 3 comprisefirst magnetic pole teeth 11 a and 12 b that are arranged in differentdirections alternately from the viewpoint of the secondary member 6.Magnetic poles 2 on the other side of the armature unit 3 comprisesecond magnetic pole teeth 21 b and 22 a that are also arranged indifferent directions (upwards and downwards, respectively, in FIG. 2)from the viewpoint of the secondary member 6.

FIG. 3 shows the overall structure of the comparative example. In orderto drive the linear motor of the structure shown in FIG. 2 smoothly, anumber M (where M is a natural number greater than 1) of M phases ofarmature units 3 must be arranged in series at such intervals that thedistance between the centers of the magnetic pole teeth at the ends ofadjacent armature units 3 is more or less k·P+P/M (where k=0, 1, 2, . .. ). In the example of FIG. 3, the number M of phases of the motor is 3,and armature units 3 of phase A, phase B, and phase C are arranged. Whenthe length of a coil end is L, the armature units 3 must be arranged atsuch intervals that the distance between the pole teeth at the ends ofadjacent armature units 3 is at least 2L.

FIG. 4 is an overall view of the linear motor according to a firstembodiment of the invention. This linear motor differs from thecomparative example in that a coil 4 is wound at two locations, namelyon both sides of the bottom of the magnetic pole teeth of the armatureunits 3. Because the coil 4 is wound separately at each side of thearmature unit, the same number of turns of the coil 4 as in thecomparative example can be obtained by winding half the number of turnsat each side. Thus, the length L′ of the coil end in the presentembodiment is half the length L of the coil end in the comparativeexample. Accordingly, the armature units 3 can be arranged more closelyto one another than they are in the comparative example, thus making itpossible to reduce the size of the armature as a whole.

FIG. 1 shows an overall view of the linear motor according to a secondembodiment of the invention. In this embodiment, while it is possible toarrange a coil 4 on either side of an armature unit 3, as in the firstembodiment, the coil 4 is disposed at one side of the coil core in eachof the adjacent armature units 3 in an alternating fashion. The lengthL″ of the coil end in the present embodiment is substantially the sameas the length L in the comparative example. However, because the coils 4of the adjacent armature units 3 are disposed at opposite sides, thearmature units can be arranged more closely than they are in thecomparative example, thus making it possible to reduce the size of thearmatures as a whole.

While in the first embodiment it is necessary to arrange the coils attwo locations in each armature unit 3, in the second embodiment it isonly necessary to arrange the coil 4 at one location in each armatureunit 3. Thus, the productivity of the armature can be increased whilereducing its size, and manufacturing costs can be reduced.

While in the above-described comparative example and embodiments thesecondary member 6 is transported, the present invention can be alsoapplied to cases where the armature is transported. Furthermore, whilethe permanent magnets 34 are disposed in the secondary member 6 in theabove example and embodiments, the secondary member 6 may comprise aflat board made of a magnetic material and having an uneven surface, ora flat board made of a conductor.

Thus, in accordance with the invention, the coil is disposed at twolocations on either side of the coil portion of the armature unit. Thusthe length of the coil end can be shortened and the armature units canbe arranged more closely to one another, making it possible to reducethe size of the armatures as a whole.

Further, because the coil is arranged on opposite sides of the core ofthe coil portion in the armature units alternately, the armature unitscan be arranged more closely to one another, thus making the armatureunits compact as a whole. As it is only necessary to arrange the coil atone location in each armature unit, the productivity of the armature canbe increased while reducing manufacturing costs.

1. A linear drive apparatus comprising: a plurality of armature unitseach comprising a magnetic material on which a coil made of a conductoris disposed; and an armature comprising the multiple armature unitsarranged in a row, wherein the armature unit comprises a plurality ofopposing portions comprising opposing magnetic pole teeth, the magneticpole teeth being arranged in an interdigitated manner between adjacentopposing portions, wherein a secondary member is disposed between themagnetic pole teeth constituting the opposing portions, and wherein thearmature units comprise coils disposed at least two locations thereof.